Self-piercing nut element and componet assembly consisting of the nut element and a sheet metal part

ABSTRACT

A piercing nut element having a strength in the range between 700 and 900 MPa which is designed to be pressed into the sheet metal part. The nut element is characterized in that the self-piercing attachment of the nut element into a sheet metal part of higher strength, or into a sheet metal part with a thickness greater than 3.5 mm, the nut element is designed in such a way that the piercing section has a peripheral extending groove below the sheet metal contact surface and in that the piercing section has a piercing edge at its free end face with the piercing edge being spaced from the boundary of the groove adjacent to the piercing section by a peripheral surface having an axial height which corresponds to at least 30% and preferably to at least 50% of the sheet metal thickness, wherein the radial wall thickness of the piercing section in the region of its free end face from the outer side of the piercing section up to the nominal diameter of the thread corresponds to a thickness between 1.2 to 1.8 and preferably 1.5 times the intended sheet metal thickness.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation Application of U.S. application Ser.No. 12/874,092, filed Sep. 1, 2010, which claims priority of GermanPatent Application No. 10 2009 039 817.1, filed Sep. 2, 2009, thedisclosure of which is expressly incorporated by reference herein intheir entireties.

FIELD OF THE INVENTION

The present invention relates to a self-piercing nut element having astrength in the range between 700 and 900 MPa which is designed to bepressed into a sheet metal part with the nut element having thefollowing features: a head part forming a flange, a central bore in thehead part which is designed to receive a bolt element and which has acentral longitudinal axis, a sheet metal contact surface formed in aplane at least substantially perpendicular to the central longitudinalaxis at the flange, as well as a piercing section extending away fromthe head part at the side of the sheet metal contact surface in thedirection of the longitudinal axis. Furthermore, the present inventionrelates to a component assembly consisting of such a nut element whichis attached to a sheet metal part.

BACKGROUND OF THE INVENTION

In the field of fastener elements which are attached during themanufacture of sheet metal parts to these by machines and distinguishesbetween pressing elements, on the one hand, and rivet elements, on theother hand. Pressing elements are characterized in that they are atleast not intentionally be deformed on attachment to a sheet metal partbut rather the sheet metal part itself is deformed and brought intoengagement with features of shape of the pressing element, whereby thepressing element is attached in a manner secure against rotation andpress-out at the sheet metal part. For rivet elements the element isintentionally deformed during attachment of the sheet metal part, mainlyin order to form a rivet bead, whereby the sheet metal part is trappedbetween the rivet bead and a flange part in order to achieve aconnection here which is also secured against rotation and press-out.

Furthermore, both pressing elements and also rivet elements are known asself-piercing elements. The designation self-piercing is to beunderstood such that the corresponding element pierces its own hole inthe sheet metal part, naturally only when an adequate force is exertedon the self-piercing element, for example by a press or by a robot or byforce-actuated tongs which press the self-piercing elements against thesheet metal part and which support the sheet metal part at the sideremote from the element on a corresponding die button.

In vehicle construction it was hitherto customary to use self-piercingelements with sheet metal parts which have a strength below about 300MPa. The self-piercing elements which are then used usually have a inaddition strength in the range between 700 and 900 MPa and inexceptional cases of up to about 1250 MPa, which is entirely sufficientin order to pierce a hole in the sheet metal part on attaching thefastener element to the sheet metal part, in particular when the sheetmetal part has a thickness of below about 3 mm. Strengths of theelements of up to about 850 MPa apply for example for elements of theclass 8 whereas higher strengths apply for elements of the classes 10and 12 which normally make a heat treatment and/or a specific materialselection of the corresponding elements necessary.

With the fastener elements that are used, the material of the fastenerelement in the raw state normally has a strength of about 380 MPa. Thisstrength is however increased to values in the range between 700 and 900MPa solely by the cold deformation which is used in order to producefastener element by cold deformation starting from the bar material.

For some purposes fastener elements are required which have a higherstrength than 900 MPa. These are then manufactured from a material whichcan be hardened by a heat treatment, whereby a higher strength isachieved. However, such heat treatments are undesired in many cases.They represent a different process in comparison to manufacture offastener elements with cold deformation and are normally not evencarried out in the same factory in which the fastener elements aremanufactured, whereby a considerable expenditure of time and money isrequired in order to produce heat treated elements of higher strength.

On the other hand, sheet metals with higher strength are increasinglybeen used in vehicle construction and partly also heat-treated sheetmetal parts which have strength above the normal range of strength of700 to 900 MPa for fastener elements. Such sheet metal parts of higherstrength make it possible, on the one hand, to operate with thinnersheet metals, whereby weight can be saved, but, on the other hand, makesit extremely difficult to operate with self-piercing elements.

Sheet metal parts of higher strength are also required in vehicleconstruction which have larger thicknesses, since in some positions inthe vehicle applications arise in which a thicker sheet metal part or ahigher strength sheet metal part can be used to advantage.

Furthermore, interest exists currently in vehicle construction ofoperating at certain positions with sheet metal parts having a thicknesslarger than 3.5 mm, with the sheet metal parts then having strengthswhich lie in the above-named region of 300 MPa. An example for suchapplications is in the chassis area of trucks.

SUMMARY OF THE INVENTION

The present invention is based on the object of providing aself-piercing nut element which, with a strength in the range between700 and 900 MPa, can be introduced in self-piercing manner into sheetmetal parts of higher strengths or with thicknesses greater than 3.5 mm.Such nut elements in accordance with the invention are largely press-inelements. Furthermore, the nut element of the invention or the componentassembly of the invention should be capable of being manufactured atrelatively favorable cost.

In order to satisfy this object provision is made in a nut element ofthe initially named kind in that the self-piercing attachment of the nutelement into a sheet metal part of higher strength, or into a sheetmetal part with a thickness greater than 3.5 mm, the nut element isdesigned in such a way that the piercing section has a peripheralextending groove below the sheet metal contact surface and in that thepiercing section has a piercing edge at its free end face, with thepiercing edge being spaced from the boundary of the groove adjacent tothe piercing section by a peripheral surface having an axial heightwhich corresponds to at least 30% and preferably to at least 50% of thesheet metal thickness, wherein the radial wall thickness of the piercingsection in the region of its free end face from the outer side of thepiercing section up to the nominal diameter of the thread corresponds toa thickness between 1.2 to 1.8 and preferably 1.5 times the intendedsheet metal thickness.

The corresponding component assembly existing of self-piercing nutelement and the sheet metal part is characterized in that the sheetmetal part has a pierced hole having a shape corresponding to the shapeof the piercing section; in that the material of the sheet metal part atthe side of the sheet metal part remote from the sheet metal contactsurface has a recess adjacent to the piercing section and surroundingthe piercing section and in that the material of the hole rim isdisplaced into the groove as a result of the formation of the recess.

It has namely been surprisingly found in accordance with the inventionthat with a suitable design of the piercing section in the sense thatthis is provided with an at least substantial cylindrical section withan axial height which corresponds to at least 50% of the sheet metalthickness and preferably more, is also able to punch a hole in the sheetmetal part when the sheet metal part has a higher strength in the rangeof greater than 900 to over 1600 MPa and preferably of 1500 MPa or whenthe sheet metal part has a thickness greater than 3.5 mm.

The invention is however not only exhausted in the punching out of thecorresponding punched hole, but rather the sheet metal part must be sosecured to the nut element after the manufacture of the punched holethat the nut element contacts the sheet metal part in a manner secureagainst rotation and press-out.

For this purpose the preferably extending groove is provided inaccordance with the invention at the piercing section beneath the sheetmetal contact surface. It was found that even with higher strength orthicker sheet metals it is entirely possible to deform sheet metalmaterial in the region of the hole rim by means of a die button with acorresponding ring nose such that a recess arises adjacent to thepierced section and the displaced sheet metal material of the hole rimis then urged into the peripheral extending groove. Thus, as a result ofthe displacement, a considerable hole friction initially arises whichtakes care of the security against rotation. Since the sheet metalmaterial is deformed into the peripheral extending groove and this isframed, on the one side, by the sheet metal contact surface and, on theother side, by the region of the piercing section at the side of thesheet metal part remote from the sheet metal contact surface, a ratheraxial press-out resistance is effected.

If a higher security against rotation is desired, then this can berealized in different ways and means. One possibility consists inproviding the sheet metal part and/or the functional element with anadhesive layer, for example an adhesive layer which cures at highpressures. Correspondingly high pressures arise during the attachment ofthe fastener element to the sheet metal part whereby the securityagainst rotation can be achieved or favored.

Another possibility consists in making the piercing section or thegroove polygonal in plan view with rounded corners at the transitionsfrom one side of the polygon to the next. Through the polygonal shape ofthe piercing section or of the groove a high security against rotationis ensured.

The head part can also have a polygonal shape corresponding to thepolygonal shape of the piercing section and also of the groove, likewisewith rounded corners. The rounded corners are important becauseparticularly with higher strength sheet metal parts the sharp edgeswhich would otherwise arise at the transition from one side of thepolygon to the next would lead to a considerable danger, which shouldnot be underestimated, of fatigue cracks forming and of the connectionwhich is aimed at with the nut element failing in operation. Through therounded shape of the head part it is, moreover, ensured that nostress-increasing deformations of the sheet metal part occur at theradially outer side of the sheet metal contact surface, whereby theworking life could be reduced.

In order to reasonably exploit this polygonal shape of the piercingsection and of the groove or of the head part, it should be selectedfrom the group consisting of square, rectangular, pentagonal orhexagonal.

In one embodiment in which the piercing section and the groove have apolygonal shape the possibility also exists of designing the head partin plan view so that the alignment of the head part about thelongitudinal axis of the element can be ensured since with a polygonalshape of the piercing section or of the groove the piercing die musthave a corresponding shape or a corresponding piercing opening and theelement must then necessarily be aligned angle-wise with the die button.Such an alignment of the element can, for example, be achieved by twoconical depressions in the side of the head part remote from the sheetmetal part, with corresponding conical projections at the plunger of thesetting head engaging into the conical depressions and serving for acorresponding positioning of the element. One or two grooves or ribs atthe periphery of the head part could also be considered as an alignmentaid.

However, the possibility also exists of designing the entire nut elementsuch that the piercing section or the groove and the head part are atleast substantially circularly round in plan view.

Other measures must then be taken in order to ensure the securityagainst rotation. For example, this can take place in that nosesproviding security against rotation are provided which either have theform of ribs extending in the axial direction at the piercing sectionwhich can be arranged at the cylindrical section and/or in the groove orwhich can have the shape of radially extending ribs within the groovewhich are substantially triangular in side view. These ribs providingsecurity against rotation and noses providing security against rotationthen lead to a corresponding deformation of the sheet metal part on theattachment of the nut element at the sheet metal part through which thesecurity against rotation is ensured.

Furthermore, the possibility also exists in accordance with the Europeanpatent application 05 013 265.3 of producing features providing securityagainst rotation in the sheet metal part before the nut element issecured to the sheet metal part whereby the required security againstrotation can likewise be achieved.

At this point reference should be made to various documents relating tothe prior art. The old US document U.S. Pat. No. 3,775,791 disclosesfastener elements which are approximately square in plan view and whichhave grooves at two opposite sides which are intended to receive sheetmetal materials. Elements shown in FIG. 12 of the named document areintended for self-piercing introduction into a sheet metal part.However, no hint can be taken from any of the named documents for theeffect that such elements would also be suitable for the sheet metalpart of higher strengths. In practice the opposite is the case since thesharp-edged embodiment in the region of the grooves leads to fatiguecracks in the sheet metal part and this is precisely the problem withhigher strength sheet metal parts.

WO 94/01688 discloses in FIG. 17 a nut element having a head partbetween the flange and having a rivet section which is arranged beneaththe sheet metal contact surface of a head part. The element is notintended as a self-piercing element and, in addition, it has noperipherally extending groove above a piercing section. The taperedshape of the rivet section admittedly forms a groove-like recess aroundthe piercing section but this recess only extends in the axial directionof the head part further into the head part with the radially extendingribs at the sheet metal contact surface of the head part which ensurethe security against rotation. Such ribs providing security againstrotation are however not utilizable with sheet metal of higher strengthbecause, as a result of the softer material of the head part, they arepressed flat on the attachment of the nut element to the sheet metalpart. In other respects the recess then no longer corresponds to theperipherally extending groove at a piercing section beneath the sheetmetal contact surface.

The element in accordance with U.S. Pat. No. 3,253,831 is admittedlyformed as a self-piercing element, but here the corresponding groove isalso not arranged beneath the sheet metal contact surface but thisrather located axially within the head part of the element. The elementof this U.S. patent document is also not intended for the use withhigher strength sheet metal parts or thicker sheet metal parts.

FR-A-2 598 189 is also concerned with a press-in element. However, thecorresponding groove here is also arranged offset significantly withinthe head part of the element, with the region of the head part radiallyoutside of the groove being pressed into the sheet metal part itself,whereby an undesired thinning of the sheet metal part arises. Theelement in accordance with the French document is also not intended as aself-piercing element and is also not suitable for use with higherstrength sheet metal parts.

Finally, reference should be made to EP-B-1 690 013. This shows aself-piercing nut element which can be used with different sheet metalthicknesses. However, the nut element has a relatively complicated shapeand is not suited, intended or designed for uses with higher strengthsheet metal parts.

Preferred embodiments of the nut element and of the component assemblyof the present invention can be seen from the subordinate claims andalso from the following description of examples with reference to theaccompanying drawings in which the following is shown, in each case toscale:

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1A-1C representations of a first embodiment of a nut element inaccordance with the invention in a perspective view (FIG. 1A), in anaxial view of the left-hand side of the element in FIG. 1A (FIG. 1B) andin a side view of the element in accordance with the invention partly inaxial half section (FIG. 1C),

FIG. 2A the tools which are used to attach the nut elements of theinvention in accordance with FIG. 1A to a sheet metal part,

FIG. 2B a view corresponding to FIG. 1C but with the nut element securedto the sheet metal part,

FIG. 2C an enlarged representation of the form-fitted connection betweenthe nut element of the invention and the sheet metal part of FIG. 2B,

FIGS. 3A-3C,

FIGS. 4A-4C,

FIGS. 5A-5C representations corresponding to FIGS. 1A-1C but ofdifferent nut elements in accordance with the invention,

FIG. 6A a representation corresponding to FIG. 2A but of tools which areused when the nut element in accordance with the invention is attachedto a relatively thin sheet metal part,

FIGS. 6B, 6C representations corresponding to FIGS. 2B and 2C but forthe component assembly consisting of a relatively thin sheet metal partand an element in accordance with the invention,

FIG. 7A modified tools which can be used,

FIG. 7B a plan view of the component assembly produced using the tool ofFIG. 7A showing the section plane C-C,

FIG. 7C the section drawing corresponding to the section plane C-C inFIG. 7B,

FIG. 7D an enlarged representation of the encircled region of therepresentation in accordance with FIG. 7C,

FIG. 8A, 8B a perspective representation of the component assembly whichresults when the nut elements in FIGS. 1A-1C are attached to arelatively thick sheet metal part and indeed from above in FIG. 8A andfrom below in FIG. 8B,

FIGS. 9A, 9B representations corresponding to FIGS. 8A and 8B but with arelatively thin sheet metal part,

FIGS. 10A, 10B drawings corresponding to FIGS. 8A, 8B, but with thearrangement of a nut element in accordance with FIGS. 1A-1C in or on arecess in the sheet metal part,

FIGS. 11A, 11B representations corresponding to FIGS. 2B and 2C but whenusing a nut element with ribs providing security against rotation in thegroove and also at the peripheral surface of the piercing sectionbeneath the groove,

FIGS. 12A-12C representations corresponding to FIGS. 1A-1C but of a nutelement in accordance with the invention with ribs providing securityagainst rotation which extend axially along the piercing section andindeed at the peripheral surface and in the groove, and

FIGS. 13A-13C representations corresponding to FIGS. 12A-12C but with adifferent arrangement of the ribs providing security against rotation.

DETAILED DESCRIPTION OF THE INVENTION

The FIGS. 1A to 1C show first of all a first embodiment of aself-piercing nut element 10 in accordance with the invention having astrength in the range between 700 and 900 MPa, in exceptional cases ofup to 1250 MPa which is designed to be pressed into a sheet metal part,with the nut element having the following features:

A head part 14 forming a flange 12, a central bore 16 in the head part14 which serves to accommodate a bolt element (not shown) and which hasa central longitudinal axis 18, a sheet metal contact surface 20 formedin a plane standing at least substantially perpendicular to the centrallongitudinal axis 18 at the flange 12 and also a piercing section 22extending away from the head part at the side of the sheet metal contactsurface in the direction of the longitudinal axis. The bolt element canfor example be a threaded bolt, whereby the nut element 10 is providedhere with a thread cylinder 24, i.e. the bore 16 is a threaded bore.However, it could also be a bolt in the form of a bearing pin. In thiscase the thread cylinder is replaced with a smooth bore. The bore couldhowever initially be executed as a smooth bore and be so dimensionedthat a thread forming or thread cutting bolt can be used.

For the self-piercing attachment of the nut element 10 into a sheetmetal part of higher strength or onto a sheet metal part with athickness greater than 3.5 mm the nut element is designed such that thepiercing section 22 has a peripheral extending groove 26 beneath thesheet metal contact surface 20, i.e. at the side of the sheet metal partadjacent the head part and that further has a piercing edge 28 at itsfree end face 30, with the piercing edge 28 being spaced from thisadjacent boundary 32 of the groove 26 by a peripheral surface 34 havingan axial height h which corresponds to at least 50% of the sheet metalthickness. The upper boundary of the groove 26 lies here, as in allfurther embodiments in accordance with the invention in the same planeas the sheet metal contact surface.

The self-piercing nut element of FIGS. 1A to 1C and also all further nutelements disclosed here corresponding to the present teaching are inparticular for use with sheet metal parts having a strength in the rangefrom greater than 900 to over 1600 MPa, preferably of about 1500 MPa. Itis important that sufficient material is present behind the piercingedge, i.e. at the head part side of the piercing edge 28 in the regionof the named peripheral surface 34. Furthermore, the piercing sectionshould itself be designed, i.e. that a radial thickness and an axialheight h such that no undesired deformation occurs under the punching-inforces. In practice that signifies that the axial height h and theradial thickness r of the piercing section should be dimensioned asfollows:

The axial height of the named peripheral surface should correspond to atleast 30% and preferably at least 50% of the sheet metal thickness, withaxial heights of up to 100% of the sheet metal thickness and indeedbeyond this being possible, if the element is not be attached to thesheet metal part within a recess. It is important as a rule that thefree end face does not project beyond the side of the sheet metal partremote from the head part with the free end face normally being set backby about 0.02 mm relative to the named side of the sheet metal part. Inthis way a further component can be directly screwed onto the sheetmetal part and a desired direct clamping of the component with the sheetmetal part is achieved. This signifies, however, that the axial heightof the piercing section, i.e. the peripheral surface together with thegroove, may not be greater than 100% of the sheet metal part thickness,unless the nut element is attached to the sheet metal part within arecess. In this case the selection of the axial depth of the recessalways enables an arrangement in which the free end face of the piercingsection of the nut element is always set back from the plane of the sideof the sheet metal part outside of the recess remote from the head partof the nut element and indeed independently of the respective sheetmetal part thickness.

The radial wall thickness r of the piercing section in the region of itsfree end face from the outer side up to the nominal diameter of thethread (i.e. the outer diameter of the thread, i.e. when M8 tread with adiameter of 8 mm and a radius of 4 mm) lies in the range between 1.2 and1.8 times and preferably between 1.3 and 1.7 times and in particular byapproximately 1.5 times of the intended sheet metal part thickness.

If the radial wall thickness r is selected to be too small, the dangerexists of undesired deformation of the piercing section, in particularwith unfavorable circumstances resulting from tolerances. If, incontrast, it is selected to be too large, then the nut element becomesunnecessarily heavy. The value of 1.5 times the sheet metal partthickness has proved to be favorable.

With non-square or circular piercing sections the dimension r is to beunderstood as the smallest radial wall thickness, as is drawn in theFigure, then being possible to select the dimension r to be alsosomewhat smaller than 1.5 times the sheet metal part thickness, forexample 1.2 times the sheet metal part thickness.

FIG. 2A shows schematically the tools which are used in order to punchnut elements in accordance with FIGS. 1A to 1C of comparable elementsinto a sheet metal part 40. The tool consists of a setting head 42 whichis provided with a recess 44 which is adapted to the head shape of thenut element 10 so that the piercing section 22 projects from the lowerend face 46 of the setting head 42. The sheet metal contact surface 20of the nut element 10 lies in the same plane as the end face 46.

Setting heads of this kind are well known and are normally designed forthe automatic feeding of nut elements from a supply into the mount 44.Examples for such setting heads are amongst other things contained inthe European patent specification EP-755 749 B2 of the presentapplicant. Furthermore, the setting head could for example be used suchas is described in GB-A-934101.

Beneath the sheet metal part 40 there is located a die button 50 with acentral opening 52, the cross-sectional shape of which corresponds tothat of the piercing section 22, with the die button opening 52 beingmade slightly larger than the piercing section 22 so that the latter canfit into the opening 52 with a small clearance. For example, the opening52 could be approximately 0.01 mm larger in comparison to the piercingsection 22. The opening 52 has a central longitudinal axis 54 which isaligned with the central longitudinal axis 18 of the nut element 10.

Since the opening 52 of the die button is intended to accommodate thepiercing section 22 at least in the region of its end face, the diebutton must be aligned in the corresponding tool of the press inaccordance with the alignment of the nut 10 in the setting head.

Furthermore, it should be mentioned that the passage 56 beneath theopening 52 diverges away from this so that the piercing slug whicharises when the nut element 10 is pressed by a force acting in thedirection of the arrow F against the sheet metal part and against thedie button, whereby a piercing slug is cut out from the sheet metal partby means of the cooperation between the piercing section 22 and the diebutton 50 and is finally disposed of via the diverging passage 56. Inthis figure a so-called hold-down member (not shown) can be integratedin the setting head 42. This hold-down member has the task of pressingthe sheet metal part 40 firmly against the end face 58 of the die buttonor against the tool receiving the die button 50 prior to the punchingthrough of the sheet metal part 40.

Normally the die button 50 is accommodated in the lower tool of a pressand indeed such that the upper end face in FIG. 2A lies flush with thesurface of the lower tool. The setting head 42 is then either installedon an intermediate plate of the press or on the upper tool of the press.It is equally possible to accommodate the die button 50 in theintermediate plate of the press and to then arrange the setting head 42in the upper tool of the press. Furthermore, inverse arrangements arealso possible in which the die button 50 is arranged above the settinghead 42, for example such that the setting head 42 is arranged facingupwardly in the lower tool of the press or in the intermediate plate ofthe press, the die button then consequentially will be arranged in theinverse position relative to FIG. 2A in the intermediate plate of thepress or in the upper tool of the press.

Finally, it is not necessary to use a press to punch or stamp-in the nutelement 10 but rather this function could be taken on by a robotequipped with corresponding tools by force-actuated tongues.

Around the opening 52 of the die button there is a nose 60 which in planview has a square shape with rounded corners corresponding to theperipheral line of the piercing section 22. The nose 60 has a verticalflank 61 which surrounds the opening 52 and an oblique flank 63.

On closing of the press or of the tool in accordance with FIG. 2A, thepiercing section 22 pierces a piercing slug from the sheet metal part 40which then drops through the passage 56 of the die button and can beremoved from the press. The punching through of the sheet metal parttakes place as a result of shear forces which arise between the piercingedge 28 of the piercing section 22 and the boundary of the opening 52 atthe upper side of the die button.

During the punching through of the sheet metal part, the ring nose 60also presses directly against the underside of the sheet metal part andforms there a recess 62 which extends around the piercing section 22 inthe region of its end face edge. The material which arises during theformation of the recess 62 is forced as a result of the considerablecompression ring press, to flow into the groove 26 whereby the sheetmetal part 40 is connected in form-fitted manner to the nut element 10.The nut element 10 is namely secured against rotation about the axis 18in the sheet metal part because here the square form of the piercingsection 22, which is arranged in a punched-out opening in the sheetmetal part 40 of matched shape, prevents a mutual rotation of the sheetmetal part and of the nut element. Through the material which is locatedin the groove 26 not only is a high hole friction produced between thesheet metal part and the nut element which also contributes the securityagainst rotation but rather a form-fitted connection is also producedsuch that the pressing out of the nut element out of the sheet metalpart 40 in the pressing out direction 66 is not possible or is onlypossible with the application of considerably destroying forces. Thedanger that the nut element 10 is pressed downwardly into the oppositedirection (opposite to the direction of travel 66) is not presentbecause the sheet metal contact surface 20 sits over its full area onthe surface of the sheet metal part 40 and prevents this.

The overlap in the region of the groove of the piercing section is shownto a larger scale in FIG. 2C. In operation a further component isattached to the lower side of the sheet metal part 40 in FIG. 2A andindeed by means of a threaded bolt, the thread of which is screwed intothe thread 24 coming from below in FIG. 2B. One sees from the drawingsof the FIGS. 2B and 2C that the lower end face 30 of the piercingsection 22 is slightly set back relative to the under-side 68 of thesheet metal part. This signifies that in the bolted up situation, i.e.when a further component is secured by means of the above-named threadedbolt to the sheet metal part 40, the end face 30 of the nut element isso positioned that the sheet metal part 40 and the further component lieareally against one another, at least in the region of the nut element10, and are clamped again one another in the sense of a high qualitybolted connection.

The self-piercing nut element in accordance with the present teaching ispreferably so de-signed that the piercing section or the groove arepolygonal in plan view with rounded edges 36 and 36′ at the transitionfrom one side of the polygonal to the next. In the example of FIGS. 1Ato 1C the polygonal form is square. In the nut element in accordancewith FIGS. 3A to 3C it is pentagonal. In FIG. 4A to 4C it is rectangularwith two different side lengths. Otherwise, the description of FIGS. 1Ato 1C also applies to FIGS. 3A to 3C and 4A to 4C which is why the samereference numerals are also used there and the previous description alsoarise for these embodiments. One notes also in all these embodimentsthat the head part 14 in plan view also has a polygonal formcorresponding to the polygonal form of the piercing section 22 and thegroove 26, likewise with rounded corners 36″. The transitions 38, 38′from the sheet metal contact surface 20 into the side wall of the headpart, i.e. from the side wall of the head part 14 into the end face 39of the nut element remote from the piercing section, are preferablyrounded, a shape which can straightforwardly be produced to themanufacture of the nut elements by cold heading, with the rounded edges38 particularly contributing to the fact that no fatigue cracks arise atthe surface of the sheet metal part adjacent to the head part 14.

One can see from a comparison of FIGS. 1A to 1C, FIGS. 3A to 3C andFIGS. 4A to 4C that the axial height of the piercing section or of thenamed peripheral surface 34 is matched to the respective sheet metalpart thickness. Whereas the nut elements in accordance with the FIGS. 1Ato 1C, FIGS. 3A to 3C and FIGS. 4A to 4C are designed for rather thickerhigh strength sheet metal parts of 2.0 mm thickness, FIGS. 5A to 5C showa nut element 10 similar to that of FIGS. 1A to 1C which is, however,designed for thinner high strength sheet metal parts, for example forthose with sheet metal part thickness of 0.5 mm. In distinction to thenut element in accordance with FIGS. 1A to 1C it is in principle onlythe axial height h′ of the named peripheral surface of the piercingsection 22 and also the axial height of the groove 26 which are bothexecuted in the adaptation to the sheet metal part. The FIGS. 5A to 5Chave the same reference numerals as the FIGS. 1A to 1C and the previousdescription applies equally for the corresponding features. The nutelement 10 in accordance with FIGS. 5A to 5C is introduced into thesheet metal part 40 in accordance with FIG. 6A by means of the toolsshown there which are designed precisely in the same way as the tools ofFIGS. 2A to 2C which is why the same reference numerals are used here,with the previous description applying exactly in the same way for thecorresponding features.

The single important distinction between the embodiment of FIGS. 2A to2C and FIGS. 6A to 6C lies in the fact that the peripheral extendingnose 60 of the die button by way of matching to the smaller height ofthe piercing section likewise has a smaller height. The finishedcomponent assembly in accordance with FIGS. 6B and 6C is designed inprecisely the same way as the finished component assembly in accordancewith FIGS. 2B and 2C, i.e. the end face 30 of the piercing section 22stands slightly behind the side 68 of the sheet metal part 40 remotefrom the sheet metal contact surface 20 in order to comply with theattachment situation as previously described.

The FIGS. 7A to 7D show a further possibility for the attachment of thenut element into a sheet metal part 40, here a sheet metal part ofmedium thickness, however, this embodiment can be used for all sheetmetal thicknesses which come into consideration, for example from about0.5 to 2.0 mm for high strength sheet metal parts or up to 3.5 mm andbeyond for thick sheet metal parts of normal strength. In this examplethe sheet metal part is provided with a recess 70, with the side 72 ofthe sheet metal part 40 remote from the sheet metal contact surface 20lying directly outside of the recess 70 in a plane E and the free endface 30 of the piercing section 22 lying within the recess 70 before theside 76 of the sheet metal part remote from the sheet metal contactsurface 20 and projecting within the recess 70 but being set back fromthe named plane E.

In order to enable this embodiment, tools similar to those of FIGS. 2Ato 2C or 6A to 6C can be used but with certain modifications which willnow be explained in more detail.

In conjunction with the FIGS. 7A-7D the same reference numerals are usedfor features or parts as previously which have the same design orfunction. Only the different parts or features will be especiallydescribed. It will be understood that the previous description appliesfor parts and/or for features which are identified with the samereference numeral in just the same way for this embodiment.

First of all it is evident from FIG. 7A that the nut element 10 is nowarranged somewhat further to the setting head 42 and that the lower sideof the setting head around the functional element has a recess 80matched to the shape of the recess 70. The base surface 82 of the recessis now aligned with the sheet metal contact surface 20 of the nutelement 10. The sheet metal part 40 with the recess 70 is arrangedbetween the setting head 42 and the die button 50 and one can see fromFIG. 7A that the recess 70 has been previously manufactured in anearlier processing step. This is, however, not compulsorily necessary aswill be explained in the following.

In any event the recess 80 in the lower end of the setting head is sodesigned that it corresponds to the outer contour 74 of the recess 70,i.e. to the shape above the sheet metal part 40 in FIG. 7A

The recess 70 in the sheet metal part 40 also makes it necessary thatthe die button be modified and indeed in such a way that the peripheralnose 60 is now located on a ring step 88 which is matched to the innershape of the recess in accordance with FIG. 7A. In this embodiment thepunching through of the sheet metal part 40 takes place in the region ofthe base 90 of the recess and indeed precisely as previously described.

The component assembly situation can be found in FIGS. 7C to 7D with thesectional drawing in accordance with FIG. 7C being taken in accordancewith the section line C-C of FIG. 7B. As a result of this section plane,which is taken at the left side of FIG. 7B through the rounded corner ofthe piercing section, the nut element 10 has a larger radial dimensionto the left of the central axis 18 of FIG. 7C than to the right side ofFIG. 7C where the section plane is taken through the center of astraight side of the piercing section 22 which is square in plan view.

One can see from FIG. 7C that here the sheet metal part 40 completelyfills the recess of the groove 26 and that the ring-like groove 62 inthe sheet metal part is arranged in the lower region of the base part 90of the recess 70. One can also see from FIGS. 7C to 7D that in thisembodiment the peripheral surface 34 of the piercing section 22 isexecuted with axial height which is indeed fractionally larger than thatof the sheet metal thickness. This ensures that the piercing section 22as adequately stable in order to punch through the sheet metal part 40.Since the groove 26 receives the sheet metal part here the peripheralsurface 34 of the piercing section 22 lies below the side 76 of the baseregion 90 of the sheet metal part 40 remote from the sheet metal contactsurface of the element but still within the recess 70. Thus, the desiredbolted up situation is ensured when bolting a further component to thelower side of the sheet metal part in FIGS. 7C and 7D since the sheetmetal part 40 and the further component lie areally against one anotheroutside of the recess. On tightening the threaded bolt, the nut element10 is drawn against the further component in the sense of apre-stressing of the sheet metal material of the recess 70 so that thefurther component also press against the end face 30 of the piercingsection 22. It should be pointed out that the amount by which the endface 30 is set back from the plane of the sheet metal part outside ofthe recess (the lower side of the sheet metal part outside of therecess) is relatively small in practice and normally dimensioned to bebetween 0 and 0.02 mm. Although FIGS. 7A to 7D show the use of a sheetmetal part 40 with a pre-manufactured recess 70 this is not compulsorilynecessary. One can operate in just the same way with a flat sheet metalpart 40 with the recess then being simultaneously manufactured with thepunching in of the nut element 10.

The FIGS. 8A and 8B show in a perspective illustration the situationwhich exists when the nut element 10 is introduced into a sheet metalpart without a recess. From FIG. 8A one can see that the head part 14 ofthe nut element 10 lies in the surface of the sheet metal part 40 butdoes not project into this surface. FIG. 8B shows the sheet metal partin accordance with FIG. 8A from below. Here it is evident that the endface 30 of the nut element does not project beyond the side of the sheetmetal part which is remote from the sheet metal contact surface 20 ofthe nut element 10.

The FIGS. 9A and 9B show the same situation but here with a thinnersheet metal part while using the nut element 10 in accordance with FIGS.5A to 5C. There the sheet metal contact surface 20 of the head part 14of the nut element lies on the surface of the sheet metal part in FIG.9A without the head part being arranged offset in the sheet metal part40. In FIG. 9B it is also evident that the end face 30 of the nutelement 10 does not project beyond the corresponding side of the sheetmetal part.

The FIGS. 10A and 10B then show the corresponding arrangement when usinga recess. There the sheet metal contact surface 20 of the nut element 10lies on the top side of the base surface of the sheet metal part 40 inFIG. 10A whereas it is evident from FIG. 10B, i.e. in the illustrationon the lower side of the sheet metal part of FIG. 10A that the end face30 of the nut element 10 does not project beyond the upper sheet metalside 68 of the sheet metal part in FIG. 10B.

In all embodiments the material of the sheet metal part is received inform-fitted manner in the groove 26. The reference numerals that areotherwise used are to be understood in the same way as previously, i.e.the previous description applies in just the same way for the featuresof shape which are characterized with the same reference numeral.

Whereas in the previous Figures the head part of the nut element 10 ispolygonal in plan view, this is not compulsorily necessary, but ratherthe head part 14 can, for example, be circularly round in plan view asshown in FIGS. 11A, 11B, 12A and 12B, and indeed either with anembodiment of the piercing section and which both the peripheral surfaceof the piercing section and also the groove are polygonal and haverounded corners as well as with a piercing section which is itselfcircularly round in plan view and approximately circularly round, asshown in FIGS. 11A, 11B, 12A and 12B.

The FIGS. 11A and 11B show further how one can use a nut element 10which is designed for a sheet metal thickness within certain limitswhich are determined by the stability of the piercing section incomparison of the sheet metal part thickness and strength also for athicker sheet metal part by designing the piercing die button in thesense that the piercing die button is designed to form a pronouncedrecess in the lower side of the sheet metal part in FIGS. 11A and 11Brespectively.

When the piercing section or the groove is made polygonal, the requiredsecurity against rotation is achieved hereby by form-locked connectionto the sheet metal part. If, however, the piercing section or the grooveare circularly round it can be necessary to take other measures toensure security against rotation. One possibility consists of providingthe nut element in the region of the sheet metal contact surface 20 andof the groove 26 with an adhesive, for example an adhesive which curesunder pressure.

Another possibility, which is shown in FIGS. 11a , 11B, 12A and 12B,consists in providing noses 90 providing security against rotation whichhave the form of ribs extending in the axial direction at the piercingsection 22 which can be arranged at the cylindrical section 34 and inthe groove 26.

When the nut element is provided with noses providing security againstrotation which have the form of ribs at the piercing section whichextend in the axial direction and which are arranged at the peripheralsurface and/or in the groove then recesses 92 providing security againstrotation are formed in the finished component assembly corresponding tothe shape of the ribs providing security against rotation in the holerim of the sheet metal part.

As an alternative to this, radially extending ribs 94 can be providedinside the groove as shown in FIGS. 13A to 13C, which are at leastsubstantially triangular in side view.

When the nut element is provided with noses 94 providing securityagainst rotation which have the form of ribs extending radially withinthe groove and which are at least substantially triangular in side viewthen the finished component assembly has recesses providing securityagainst rotation in the hole rim of the sheet metal part correspondingto the shape of the ribs providing security against rotation.

The result of the attachment of the nut element 10 in accordance withthe present teaching is a component assembly consisting of aself-piercing nut element 10 and a sheet metal part 40 and ischaracterized in that the sheet metal part 40 has a pierced hole with ashape corresponding to the shape of the piercing section 22, that thematerial of the sheet metal part 40 has at the side of the sheet metalpart remote from the sheet metal contact surface 20 and adjacent to thepiercing section a recess 62 which surrounds the piercing section andthat the material of the hole rim is urged as a result of the design ofthe recess into the groove 26.

It is particularly favorable when the sheet metal part 40 lies in oneplane in the region of the attachment of the nut element and alsoradially outside of this region and the free end face 30 of the piercingsection 22 is set back from the side remote from the sheet metal contactsurface.

At this point certain remarks are appropriate. The piercing section 22or the groove 26 can have a shape in plan view which is selected fromthe group square, rectangular, pentagonal or hexagonal.

The peripheral surface 34 can have either an axially parallel extent oran enclosed angle relative to the longitudinal axis of greater than 0°to 5° in any desired radial planes which include the longitudinal axis18, with the peripheral surface 34 of the groove 26 having a divergingextent towards the piercing edge 28.

The transition from the peripheral surface 34 to the groove 26 is eitherrounded or has the shape of an inclined surface with an included anglein the region between 30° and 75° related to the central longitudinalaxis 18 and going in the direction of the piercing section 22 to thehead part 14.

In all embodiments all materials can be named as examples for thematerial of the fastener elements which achieve the strength values ofclass 8 in accordance with the ISO standard and the contacting colddeformation, for example a 35B2-alloy in accordance with DIN 1654.

The invention claimed is:
 1. A component assembly comprising aself-piercing nut element (10) and a sheet metal part (40) having athickness, wherein the self-piercing nut element (10) has a strength inthe range between 700 and 1250 MPa, and which is designed to be pressedinto said sheet metal part (40) having a thickness, the nut elementhaving the following features: a head part (14) forming a flange (12)extending all around the nut element, a central bore (16) in the headpart having a thread with a nominal diameter which is designed toreceive a bolt element and which has a central longitudinal axis (18), asheet metal contact surface (20) formed in one plane at leastsubstantially perpendicular to the central longitudinal axis at theflange (12) and extending all around the longitudinal axis, as well as apiercing section (22) extending away from the head part at the side ofthe sheet metal contact surface in the direction of the longitudinalaxis, the nut being adapted for a self-piercing attachment of the nutelement to said sheet metal part (40), said sheet metal part having athickness greater than 3.5 mm, the piercing section (22) having aperipherally extending radial groove (26) in the piercing section andextending all around the piercing section, the groove having a boundaryspaced from the sheet metal contact surface, the piercing section notbeing intentionally deformed, and the piercing section (22) furtherhaving a free end face and a piercing edge (28) at the free end face,with the piercing edge (28) being spaced from the boundary of the groove(26) by a peripheral surface (34) having an axial height whichcorresponds to at least 30% of the sheet metal part, wherein thepiercing section has a radial wall thickness in a region of its free endface from the outer side of the piercing section up to a nominaldiameter of the thread, the radial wall thickness corresponding to athickness between 1.2 to 1.8 times the thickness of the sheet metalpart, and wherein said sheet metal part (40) has a pierced hole having ahole rim and a shape corresponding to the shape of the piercing section(22); wherein the material of said sheet metal part (40) at the side(68) of a sheet metal part remote from the sheet metal contact surface(20) has a recess (62) adjacent to the piercing section and extendingall around the piercing section (22) and wherein the material of thehole rim is displaced into the radial groove (26) all around thepiercing section as a result of the formation of the recess (62).
 2. Thecomponent assembly in accordance with claim 1, wherein the self-piercingnut element (10) has a strength in the range between 700 and 900 MPa. 3.The component assembly in accordance with claim 1, wherein said sheetmetal part (40) lies in a plane (E) in the region of the attachment ofthe nut element (10) and also radially outside of this region andwherein the free end face (30) of the piercing section (22) is set backfrom the side remote from the sheet metal contact surface (20).
 4. Thecomponent assembly in accordance with claim 1, wherein said sheet metalpart (40) is provided with a recess (70), wherein the side of said sheetmetal part (40) remote from the sheet metal contact surface (20) liesdirectly outside of a depression in a plane (E) and wherein the free endface (30) of the piercing section (22) projects within the recess (70)in front of the side (76) of said sheet metal part (40) remote from thesheet metal contact surface, but is offset rearwardly from the saidplane (E).
 5. The component assembly in accordance with claim 1, whereinwhen the nut element (10) is provided with noses (90) providing securityagainst rotation which have the shape of ribs extending in the axialdirection at the piercing section (22) which are arranged at theperipheral surface (34) and/or in the groove (26), recesses (92)providing security against rotation corresponding to the shape of theribs providing security against rotation being formed in the hole edgeof said sheet metal part (40) in accordance with the shape of the ribsproviding security against rotation.
 6. The component assembly inaccordance with claim 1, wherein when the nut element (10) is providedwith noses providing security against rotation which have the form ofribs (94) extending radially within the groove (26) and which are atleast substantially triangular in side view, recesses providing securityagainst rotation being formed in the hole rim of said sheet metal part(40) in accordance with the shape of the ribs providing security againstrotation.